I'd like to make a border with molding chocolate. Has anyone ever done this?

Yes. What did you have in mind?

Just a straight ribbon. I'm just not sure what to use to cut it to keep it straight and an even width or how to make it long enough to go around the cake. The bottom layer is a 16" square.

Good question, I would like to know the answer too. I have such a difficulty keeping ribbons made from either fondant, or chocolate straight, and the same thickness. I'll keep watching.

I bought some slide-on guide rings at a local store that carries pots and pans, measuring spoons and cups, etc. for my rolling pin. There are several sets in various thicknesses. They worked great for rolling the fondant out at all the same thickness. I started by making a "rope" and then flattening it slightly with my hands before rolling it into a strip.

Then I bought Wilton's Fondant Ribbon Cutter/Embosser Set. It worked like a charm! I used just the straight cutting wheels. The spacer kept it all the same width. I found it didn't matter if you cut the ribbon exactly straight as the chocolate has some give to it. As long as it was the same thickness and width, it worked perfectly!

Good luck with your ribbons!

I roll a rope of fondant thru my pasta roller. Then lay a yardstick on top and cut with a knife. The yardstick is the perfect width.

I bought a clay gun and extract my fondant through that! Works great. I can do one, two or more ropes and even twist them together or just one.
just be sure and use plenty of crisco so it stays moist and slides through nicely without elephant skin.

Is there a recipe for making this chocolate? I'd love to give this a try.
Thanks,
Nancy